The present invention relates to an omnidirectional visual camera for photographing an omnidirectional image that is picked up in all directions around an arbitrary viewpoint position.
If environments around a certain viewpoint can be imaged at a time, an image free from dead angles can be obtained which allows the viewing direction to be arbitrarily changed as if the viewer was at the site.
As a device for picking up such omnidirectional images, means is known which installs a reflector with a curved surface in the front of a television camera and which picks up images projected on the reflector.
Japanese Patent Laid-Open No. 9-118178 and Japanese Patent Laid-Open No. 11-174603 disclose device configurations having a reflector for allowing omnidirectional images to be picked up.
These specifications disclose that the basic configurations of these devices require, in addition to the reflector and the camera, a support member for fixing the reflector to a front portion of the camera in its optical-axis direction. They also disclose that the support member comprises a transparent material so as not to obstruct generation of a reflected image.
When an image picked up by such a device is geometrically converted, arbitrary viewing directions can be selected to generate an image like one picked up by a normal camera.
The above devices, however, have problems described below.
If the rotating center axis of the reflector is not precisely aligned with the optical axis of the camera, the image may be unexpectedly distorted; the image after the geometrical conversion may be significantly distorted to degrade the image quality. Thus, it is important how to manage the accuracy of the processing of the support member, which determines the relative positioning between the reflector and the camera, as well as the accuracy of the mounting of the support member on the reflector. This disadvantageously increases processing and assembly costs of the support member.
In particular, if the support member and the reflector are installed in a very small camera, the camera fails to provide appropriate performance and is unsuitable for mass production unless the reflector and the support member for supporting the reflector are precisely mounted in the front of the camera.
It is an object of the present invention to provide an omnidirectional visual camera that allows the rotating center axis of the reflector to be precisely aligned with the optical axis of the camera in order to obtain appropriate omnidirectional images.
An omnidirectional visual camera set forth in aspect 1 of the present invention is characterized by comprising a reflecting member including a rotating surface portion having a convex surface of a rotating secondary curved surface and a cylindrical portion having a cylindrical shape and having a rotating center axis aligning or substantially aligning with a rotating axis of the rotating surface, the rotating surface portion and the cylindrical portion being integrally molded of a transparent material so that an outer diameter portion of the rotating surface portion is inscribed in the cylindrical portion, the projecting surface of the rotating surface portion being processed into a mirror surface, and a camera having an optical axis substantially aligning with the rotating center axis of the reflecting member and installed opposite to the convex surface of the rotating surface portion, the camera picking up a reflected image reflected from the convex surface of the rotating surface portion of the reflecting member.
An omnidirectional visual camera set forth in aspect 2 of the present invention is characterized by comprising a reflecting member including a rotating surface portion having a convex surface of a rotating secondary curved surface, a cylindrical portion having a cylindrical shape and having a rotating center axis substantially aligning with a rotating axis of the rotating surface, and having a cylindrical inner diameter larger than an outer diameter of the rotating surface portion, and a connection section for connecting one longitudinal end of the cylindrical portion and the outer diameter portion of the rotating surface portion, the rotating surface portion, the cylindrical portion, and the connection section being integrally molded of a transparent material, the projecting surface of the rotating surface portion being processed into a mirror surface, and a camera having an optical axis substantially aligning with the rotating center axis of the reflecting member and installed opposite to the convex surface of the rotating surface portion, the camera picking up a reflected image reflected from the convex surface of the rotating surface portion of the reflecting member.
An omnidirectional visual camera set forth in aspect 3 of the present invention is characterized in that in aspect 2, the convex surface of the rotating surface portion has a hyperboloidal shape having an internal focus, and the connection section is configured so that an arbitrary line joining the outer diameter portion of the rotating surface portion and the internal focus together passes through the cylindrical portion.
An omnidirectional visual camera set forth in aspect 4 of the present invention is characterized in that in aspect 2 or 3, the connection section of the reflecting member or both the connection section and a surface of the rotating surface portion which is not processed into a mirror surface are processed so as to block light.
An omnidirectional visual camera set forth in aspect 5 of the present invention is characterized in that in aspect 1 or 4, one end surface of the cylindrical portion to which the rotating surface portion is connected has a smaller diameter than the other end thereof.
As described above, according to the present invention, the simple structure comprising the integrally molded reflecting member and the camera enables omnidirectional images to be photographed at a time. Accordingly, the integral molding prevents errors in the centering between the reflecting surface and the cylindrical surface, thus providing a sufficient geometrical accuracy for omnidirectional image pickup.
Furthermore, with respect to the shape of the integrally molded reflecting member, the cylindrical portion is tapered, thus providing an inexpensive omnidirectional visual camera that is suitable for mass production.
Moreover, the integrally molded reflecting member is designed so that incident light will not be blocked by the connection section, thus enabling reflected light from all the areas of the reflecting surface to be imaged properly. Accordingly, the present invention achieves the effective use of the reflecting surface and is effective in reducing the size of the device.
Further, when the surface of the reflecting member which is opposite to the camera section is coated, unwanted light is prevented from entering, thus improving the image quality of the omnidirectional visual camera.